1. Field of the Invention
This invention relates to a method for continuously taking a hot sample gas to be analyzed from a reaction chamber, wherein the sample gas is taken by means of an extraction probe and is delivered to an analyzer through an extraction line comprising at least one filter, and to apparatus for carrying out the method.
2. Description of the Prior Art
For the control of a process in dependence on the composition of the gases formed in the process, sample gas must be taken from the reaction chamber and must be delivered to an analyzer. This will be particularly difficult if the gas is hot and laden with gas, such as is the case with gases which are formed by the calcination of a ground raw mixture of raw materials in the production of cement. In that case the gas temperature in the reaction chamber are so high that the extraction probes used to take the sample gas from the reaction chamber must be cooled so that the temperature along the extraction line may fall below the dew point temperature. In that case the condensate and the entrained dust particles may form a sludge, which deposits in the extraction probe and in the filter that is connected to the extraction probe so that the deposits may restrict or block the flow paths for the sample gas. For this reason, clean-up operations are periodically required to remove the deposits from the extraction line and to clean the filter which precedes the analyzer. Such clean-up operations involve a substantial expenditure and have also the disadvantage that no gas sample can be taken from the reaction chamber during the clean-up operation so that the process cannot be controlled during that time. Besides, the gas at a relatively low rate is required for the analysis so that the sample gas takes a relatively long time to flow along the flow paths provided from the reaction chamber to the analyzer and, as a result, any change in the gas composition can be taken into account in the process control only with a substantial time lag.